In addition to the aforementioned TIA or CVA within the prior three months, high-risk patients also include those with a CHADS2 score of five or six or any patient with a history of rheumatic heart disease.3 Patients with CHADS2 scores less than five but with a TIA or CVA greater than three months in the past are high risk.7
Presence of mechanical heart valve(s). For patients with a mechanical heart valve, knowledge of the valve type and location is essential to assist hospitalists in stratifying the risk of peri-procedural thrombosis. The current ACCP guidelines consider patients with bileaflet aortic valve prostheses without additional risk factors for stroke or atrial fibrillation to be low risk.3
The guidelines define the following characteristics as medium risk for patients: the presence of a bileaflet valve with additional risk factors for stroke such as atrial fibrillation, age greater than 75, prior CVA (more than six months prior), hypertension, diabetes mellitus, or congestive heart failure.
Patients at high risk include those with aortic valve prosthesis with a caged-ball or tilting disc, patients with mitral valve prosthesis, and those with a mechanical valve with CVA or TIA during the prior six months.7
History of previous VTE. For these patients, the duration of time that has passed since their last VTE event is an important factor in helping to stratify their risk for peri-procedural thrombosis. Hospitalists should consider patients low risk if they had VTE more than one year prior to the procedure.
Medium-risk patients are those with VTE events in the preceding three to twelve months, those with recurrent VTE, those with active cancer who have received cancer therapy within six months, or patients with non-severe thrombophilias (e.g. heterogenous factor V Leiden or prothrombin gene mutation).
Hospitalists should identify high-risk patients as those with VTE that has occurred within three months or those with severe thrombophilias such as Protein C or S deficiency, antithrombin III deficiency, or antiphospholipid antibody syndrome.
Assessment of procedure-related thrombotic risk. The type of anticipated procedure itself conveys peri-procedural thrombotic risk. For example, heart valve replacement, carotid endarterectomy, or other major vascular surgeries automatically stratify patients in the high-risk category, regardless of underlying medication condition.
Assessment of bleeding risk. Hospitalists must identify any preexisting bleeding risk factors (i.e., hemophilias or thrombocytopenia) in addition to the post-procedural bleeding risks. Risk factors for increased post-procedural bleeding include: major surgery with extensive tissue injury, procedures involving highly vascularized organs, removal of large colonic polyps, urological procedures, placement of implantable cardioverter-defibrillator/pacemakers, and procedures at sites where minor bleeding would be clinically devastating, such as the brain or spine.3
Thus, communication with the proceduralist or surgeon regarding the anticipated bleeding risk is vital.
Should the patient receive bridging anticoagulation? Patients considered high risk for peri-procedural thrombosis should receive peri-procedural bridging anticoagulation therapy, while those considered low risk should not. For patients with a moderate peri-procedural risk of thrombosis, hospitalists should base the decision on individual and anticipated pre-surgical/procedural thrombotic risks.
Recent evidence suggests that bridging anticoagulation should be avoided in patients undergoing procedures with high bleeding risk who are not at high thromboembolic risk.8
Selection and pre-operative discontinuation of bridging medication. Current ACCP guidelines only support the use of unfractionated heparin (UFH) or low molecular weight heparin (LMWH) as bridging anticoagulants.3 Evidence supports the use of either intravenous UFH (goal aPTT 1.5 to two times control aPTT) or enoxaparin (1 mg/kg BID or 1.5 mg/kg once daily).9 UFH is preferred over LMWH in patients with chronic kidney disease stage IV or V due to a more predictable pharmacokinetic profile.